1. Field of the Invention
This invention relates to an image processing method and apparatus. More particularly, the invention relates to an image processing method and apparatus, for use in a facsimile machine or copier, through which an input image is separated into a variety of images, as in the manner of a character area and a non-character area, and processing the separated input image as encoding is executed for each area into which the image has been separated.
2. Description of the Related Art
A method that relies upon the distribution of high-frequency components contained in an image often is used as a method of separating the image into character and non-character areas. This method is as follows:
(1) the image is separated into m.times.n blocks; PA1 (2) edge blocks are detected by a Laplacian operation; PA1 (3) the edge blocks are counted; and PA1 (4) based upon the relationship between the number n of edge blocks and a threshold value T, the m.times.n blocks are discriminated in the following manner: a block is a character block if n&gt;T holds, and a block is a non-character image block if n.ltoreq.T holds.
Further, a color facsimile apparatus in which character areas and non-character areas are encoded by an appropriate method has been proposed see Ser. No. 631,145 (filed on Dec. 20, 1990) and Ser. No. 651,030 (Feb. 5, 1991)!.
However, a problem encountered in the prior art described above is that when the size of the m.times.n blocks is small, it is difficult to distinguish between an edge portion of a character area and an edge portion of a non-character area. This means that when an attempt is made to perform precise discrimination, a fairly large block size is required. This is disadvantageous in that large-scale hardware becomes necessary.
Furthermore, when conventional block processing of the kind described above is executed, edge detection is difficult if an edge is present at the boundary between one cell of m.times.n blocks and an adjacent cell of m.times.n blocks. A problem arises that a character area may be judged as being a non-character area.
Another problem in the aforementioned prior art is that the portion underlying a character area (namely a color or pattern underlying the character area) vanishes, resulting in part of the image information being lost.